In centralized postal sorting centers, a RADIX sorting algorithm is typically employed to sort incoming mail. This sorting algorithm requires that mail be passed through the automated sorting system several times to place the mail in a sequence corresponding to the delivery route taken by a mail carrier, i.e., sorted to delivery sequence. This sorting algorithm requires that a precise order be maintained with each pass through the sorting system. Operators must remove and store mail following one sorting sequence and return the mail to the sorter in the correct order to ensure that the RADIX sorting algorithm has not been compromised.
FIG. 1 is a schematic illustration of a conventional large scale sorting center 200 employed in most cities and states across the U.S. Mail 202 arrives at various times each day and must be periodically and routinely loaded onto trucks 204 by a particular dispatch time for delivery to other sorting centers and various postal offices. Due to the large number of mailpieces 202 sorted at a typical sorting center, multiple sorters 206, 208, i.e., flats sorters 206 and letter sorters 208, are employed to handle the daily volume of incoming mail. The mail 202 is often transported and stored via a tray storage and retrieval system 210 before, during and after each sortation sequence. That is, to facilitate transport, storage and delivery, the sorting centers are typically equipped with miles of conveyor systems, robotic tray handling mechanisms, hundreds of forklifts/lifting/retrieving apparatus and hundreds of operators for the purpose of loading, unloading, tracking, traying and delivering the mail each day. Those sorting centers that have less invested in automated equipment often employ an even greater number of staff/personnel to manage the workflow.
Accordingly, it will be appreciated that such sorting centers: (i) require a significant quantity of costly peripheral equipment, (ii) require many operators to orchestrate the flow of mail into and out of the center and (iii) occupy a significant footprint/area in terms of real estate required to house such a large quantity of equipment and personnel. With respect to the latter, floor space is required to: (a) transport the mail to and from the tray storage and retrieval system 210, (b) house the many palettes of mail trays at the input and output areas, 212 and 214, respectively and (c) produce wide aisle ways for the passage of fork lifts and other transport vehicles.
The typical or average sorting center in the United States Postal Service (USPS) system receives and sorts mail for about 713 routes and delivers the sorted mail to about 35 delivery offices. Each delivery office typically processes mail for delivery to an average of about 20-30 routes. The mail received by the sorting center may be categorized as mail (i) arriving via USPS from other sorting centers, (ii) received from large volume/bulk mailers which have been presorted to receive sorted mail discounts and (iii) mail gathered from conventional mailbox containers and/or delivery offices, i.e., collection mail. The mail is deposited at a first processing station 216 where pre-sorted mail may be moved either to the storage and retrieval system 210 or to one of the flats or letter sorting stations 206, 208. Collection mail is typically moved to a second processing station 218 and is categorized as either: machinable or non-machineable, flats-type or letter-type, and inbound or outbound mail. Having been sorted into groups, the collection mail is conveyed to either: the flats sorter, 206, the letter sorter 208, the storage and retrieval system 210, the facer/canceller system 32 or to a manual sorting station 220. Typically, about twenty percent (20%) of the total mail ingested is non-machineable, and must, therefore, be sorted manually by operators at several manual sorting stations 220.
While the investments made in automation have vastly improved sorting center operations, these investments have focused on discrete portions of the work flow e.g., transport, storage, retrieval, loading, sorting, etc. Consequently, a significant amount of manual handling still remains for the purpose of moving mail to and from each of the automated cells or operations. For example, in some sorting centers, despite the investments in automation, mail is manually handled as frequently as seventeen (17) times from the point of entry 212 to the dispatch area 214.
Further discussion of sorting center operations and an escort-based sorting system are described in commonly-owned, co-pending U.S. patent application Ser. No. 11/544,349, filed 6 Oct. 2006 entitled “Mail Sorter System and Method for Productivity Optimization Through Precision Scheduling” and U.S. patent application Ser. No. 11/544,184 filed 6 Oct. 2006 entitled “Mail Sorter System and Method for Moving Trays of Mail to Dispatch in Delivery Order” which are both incorporated herein by reference in their entirety. Examples of an escort-based system can be found in International Application WO 2006/063204 filed 7 Dec. 2005 entitled “System and Method for Full Escort Mixed Mail Sorter Using Clamps” and can also be found in U.S. Provisional application Ser. No. 11/519,630 filed 12 Sep. 2006 titled “Sorter, Method, and Software Product for a Two-Step and One-Pass Sorting Algorithm,” which are also incorporated herein by reference in their entirety. The concepts of macro-sorting are described, for example, in U.S. Provisional Application No. 60/669,340 filed 5 Apr. 2005, titled “Macro Sorting System and Method” which also is incorporated herein by reference in its entirety.
In addition to the lack of efficiency and cost associated with prior art sorting centers, escort-based sorters such as those referenced in the prior are limited in their ability to divert/transfer articles from one conveyance path to another. For example, certain sorting arrangements could benefit from a third conveyance path, e.g., a path adjacent first and second paths, to minimize the overall length and width of the escort-based sorter. However, the conveyance/diverter systems employed in prior art escort-based sorters are limited to the transfer of the escort device between adjacent pairs of conveyance paths, i.e., between first and second paths. To transfer/divert an escort device to yet another path, i.e., a third path, requires that the additional path be located downstream of the first and second paths. As such, the overall length of the escort-based sorter is increased.
In addition to the penalties in the space requirements, the efficiency of the escort based sorter is reduced or further compromised. That is, it will be appreciated that by increasing the length of the conveyance/diverter system, the time required for dispatch, i.e., to move an escort device through the sorter, is also increased. Delays in dispatch adversely impact the time available to operate the sorter, and accordingly, reduces the number of mailpieces/articles which can be sorted within a predetermined time interval.
A need, therefore, exists for an escort-based sorting system for use in a sorting center which (i) sorts mail to delivery sequence, (ii) stores all incoming mail within the sorter during a specified time interval, e.g., over the course of a twenty-four hour time period, without the need to remove, transport, store and retrieve the mail, (iii) simultaneously and/or continuously sorts inbound and outbound mail (iv) enables conveyance and transfer between multiple adjacent paths, (v) facilitates reliable transfer of escorted mailpieces across multiple interfaces (vi) optimizes the storage and utilization of space within the sorting center to reduce its footprint and/or space requirements, (vii) dispatches mail from the sorter while continuing to sort incoming mail, (viii) communicates the status of outbound mail to other sorting centers to enable improved personnel planning and scheduling, and (ix) dispatches mail just-in-time to optimize the flow of mail processed through the sorting and sorting center.